diff --git a/packages/sampler/sample-server.mjs b/packages/sampler/sample-server.mjs
index 31b83f5a3..1d5a8e7a6 100644
--- a/packages/sampler/sample-server.mjs
+++ b/packages/sampler/sample-server.mjs
@@ -9,6 +9,7 @@ import readline from 'readline';
 import os from 'os';
 
 const LOG = !!process.env.LOG || false;
+const PORT = process.env.PORT || 5432;
 const VALID_AUDIO_EXTENSIONS = ['wav', 'mp3', 'ogg'];
 
 const isAudioFile = (f) => {
@@ -54,7 +55,6 @@ async function getBanks(directory, flat = false) {
     banks[bank].push(subDir);
     return subDir;
   });
-  banks._base = `http://localhost:5432`;
   return { banks, files };
 }
 
@@ -134,8 +134,6 @@ const server = http.createServer(async (req, res) => {
   readStream.pipe(res);
 });
 
-// eslint-disable-next-line
-const PORT = process.env.PORT || 5432;
 const IP_ADDRESS = '0.0.0.0';
 let IP;
 const networkInterfaces = os.networkInterfaces();
diff --git a/packages/superdough/sampler.mjs b/packages/superdough/sampler.mjs
index 84bac3582..aaa1a8e48 100644
--- a/packages/superdough/sampler.mjs
+++ b/packages/superdough/sampler.mjs
@@ -1,4 +1,4 @@
-import { getCommonSampleInfo } from './util.mjs';
+import { getBaseURL, getCommonSampleInfo } from './util.mjs';
 import { registerSound, registerWaveTable } from './index.mjs';
 import { getAudioContext } from './audioContext.mjs';
 import { getADSRValues, getParamADSR, getPitchEnvelope, getVibratoOscillator } from './helpers.mjs';
@@ -211,7 +211,7 @@ export async function fetchSampleMap(url) {
     // not a browser
     return;
   }
-  const base = url.split('/').slice(0, -1).join('/');
+  const base = getBaseURL(url);
   if (typeof fetch === 'undefined') {
     // skip fetch when in node / testing
     return;
diff --git a/packages/superdough/util.mjs b/packages/superdough/util.mjs
index 44ec79f77..48830541a 100644
--- a/packages/superdough/util.mjs
+++ b/packages/superdough/util.mjs
@@ -114,3 +114,13 @@ export function getCommonSampleInfo(hapValue, bank) {
 export const pickAndRename = (source, map) => {
   return Object.fromEntries(Object.entries(map).map(([newKey, oldKey]) => [newKey, source[oldKey]]));
 };
+
+export const getBaseURL = (url) => {
+  try {
+    // For real URLs
+    return new URL('.', new URL(url)).href.replace(/\/$/, ''); // removes trailing slash
+  } catch {
+    // For pseudo URLS
+    return url.split('/').slice(0, -1).join('/');
+  }
+};
diff --git a/packages/superdough/wavetable.mjs b/packages/superdough/wavetable.mjs
index 01d4eb838..3659edcd0 100644
--- a/packages/superdough/wavetable.mjs
+++ b/packages/superdough/wavetable.mjs
@@ -1,5 +1,5 @@
 import { getAudioContext, registerSound } from './index.mjs';
-import { getCommonSampleInfo } from './util.mjs';
+import { getBaseURL, getCommonSampleInfo } from './util.mjs';
 import {
   applyFM,
   applyParameterModulators,
@@ -190,6 +190,7 @@ export const tables = async (url, frameLen, json, options = {}) => {
   if (url.startsWith('local:')) {
     url = `http://localhost:5432`;
   }
+  const base = getBaseURL(url);
   if (typeof fetch !== 'function') {
     // not a browser
     return;
@@ -200,7 +201,7 @@ export const tables = async (url, frameLen, json, options = {}) => {
   }
   return fetch(url)
     .then((res) => res.json())
-    .then((json) => _processTables(json, url, frameLen, options))
+    .then((json) => _processTables(json, base, frameLen, options))
     .catch((error) => {
       console.error(error);
       throw new Error(`error loading "${url}"`);